sounds like a lot of this was underground development, outside the reach of our KH11 spy cam vision. I dont recall any NK defectors who mentioned their program had been ramped up, either.
Isn't this what Iraq needs to complete their nuclear bomb??
N. Korean facilities are deep underground, probably under a huge granite rock formation. As far as I know, Americans tried to find their existence by looking at unusal amount of warm water in the suspected areas where there is no geothermal activity.
But such things can be also camouflaged, by diverting warm water out of reactor cooling system out to water coming out of factories, for example. Or creating multi-level cooling water tanks underground so that the temperature difference between adjacent tanks will not be noticeably high. If you have one tank being used to cool this reactor, it would be difficult to hide the temperature difference below the temperature of factory waste water.